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Biomedical subjects

G Criner

Publications and source records attributed to G Criner.

9 recordsLinked to original sources
PubMed1998

Effect of lung volume reduction surgery on diaphragm strength.

Since lung volume reduction surgery (LVRS) reduces end-expiratory lung volume, we hypothesized that it may improve diaphragm strength. We evaluated 37 patients for pulmonary rehabilitation and LVRS. Before and 8 wk after pulmonary rehabilitation, 24 patients had spirometry, lung volumes, diffusion capacity, incremental symptom limited maximum exercise test, 6-min walk test, maximal static inspiratory and expiratory mouth pressures, and transdiaphragmatic pressures during maximum static inspiratory efforts and bilateral supramaximal electrophrenic twitch stimulation measured. Twenty patients (including 7 patients who crossed over after completing pulmonary rehabilitation) had baseline measurements postrehabilitation, and 3 mo post-LVRS. Patients were 58 +/- 8 yr of age, with severe COPD and hyperinflation (FEV1, 0.69 +/- 0.21 L; RV, 4.7 +/- 1.4 L). Nineteen patients had bilateral LVRS performed via median sternotomy and stapling, and 1 patient had unilateral LVRS via thorascopy with stapling. After rehabilitation, spirometry and DL(CO)/VA were not different, and lung volumes showed a slight worsening in hyperinflation. Gas exchange, 6-min walk distance, maximum oxygen uptake (VO2max), and breathing pattern during maximum exercise did not change after rehabilitation, but total exercise time was significantly longer. Inspiratory muscle strength (PImax, Pdi(max combined), Pdi(max sniff), Pdi(max), Pdi(twitch)), was unchanged after rehabilitation. In contrast, after LVRS, FVC increased 21%, FEV1 increased 34%, TLC decreased 13%, FRC decreased 23%, and FRC(trapped gas) and RV decreased by 57 and 28%, respectively. PCO2 was lower (44 +/- 6 versus 48 +/- 6 mm Hg, p < 0.003) and 6-min walk distance increased (343 +/- 79 versus 250 +/- 89 m, p < 0.001), as did total exercise time during maximum exercise (9.2 +/- 1.9 versus 6.9 +/- 2.7 min, p < 0.01). Minute ventilation (29 +/- 8 versus 21 +/- 6 L/min, p < 0.001) and tidal volume (1.0 +/- 0.33 versus 0.84 +/- 0.25 L, p < 0.001) during maximum exercise increased whereas respiratory rate was lower (28 +/- 6 versus 32 +/- 7 breaths/min, p < 0.02). Measurements of respiratory muscle strength (PImax, 74 +/- 28 versus 50 +/- 18 cm H2O, p < 0.002; Pdi(max combined), 80 +/- 25 versus 56 +/- 29 cm H2O, p < 0.01; Pdi(max sniff), 71 +/- 7 versus 46 +/- 27 cm H2O, p < 0.01; Pdi(twitch), 15 +/- 5 versus 7 +/- 5 cm H2O, p < 0.01) were all greater post-LVRS. Inspiratory muscle workload as measured by Pdi TTI was lower following LVRS (0.07 +/- 0.02 versus 0.09 +/- 0.03, p < 0.03). On multiple regression analysis, increases in PImax correlated significantly with decreases in RV and FRC(trapped gas) after LVRS (r = 0.67, p < 0.03). We conclude that LVRS significantly improves diaphragm strength that is associated with a reduction in lung volumes and an improvement in exercise performance. Future studies are needed to determine the relationship and stability of these changes over time.

Diaphragm↗
PubMed1995

Comparison of diaphragm strength between healthy adult elderly and young men.

To test the hypothesis that aging is associated with a reduction in the diaphragm's force-generating capacity, we compared the maximum transdiaphragmatic pressure (Pdimax) obtained during voluntary maximal inspiratory efforts in nine young (19-28 yr) and ten elderly (65-75 yr) subjects. The relationship between Pdi and lung volume was compared in the two groups by having subjects make maximal inspiratory maneuvers at specified lung volumes (i.e., 20, 40, and 80% vital capacity). Subjects underwent symptom-limited exercise tests to characterize their aerobic capacities and evaluate the relationship between aerobic capacity and Pdimax. The average Pdimax of the elderly subjects (128 +/- 9 cm H2O) was significantly lower (p < 0.003) than the average Pdimax of the younger subjects (171 +/- 8 cm H2O). In the elderly, Pdi was lower across the range of lung volumes tested (p < 0.001), and Pdimax occurred at similar relative lung volumes (elderly, at 47% total lung capacity [TLC]; young, at 50% TLC) in both groups. The elderly subjects were quite fit based on their VO2max, and there was no significant relationship between Pdimax and VO2max. This study suggests that diaphragm strength is reduced in elderly individuals. This age-related decrease in diaphragm strength may predispose elderly patients to diaphragm fatigue in the presence of conditions that impair inspiratory muscle function or increase ventilatory load.

Adult↗
PubMed1989

Controlled trial of external negative pressure ventilation in patients with severe chronic airflow obstruction.

The effect of intermittent external negative pressure ventilation (ENPV) with the Emerson Pulmowrap ventilator upon leg cycle endurance time (ET), maximal transdiaphragmatic pressure (Pdimax), breathing pattern as expressed by the tension time index (TTdi), and sense of well being was studied in 16 patients with severe chronic airflow obstruction (CAO). The patients were randomized to 3 wk of in-hospital pulmonary rehabilitation (Group I, seven patients) or the same program plus ENPV (Group II, nine patients). Both groups were similar in terms of age (65 +/- 8 versus 61 +/- 13 yr), severity of CAO (FEV1 of 0.64 +/- 0.14 versus 0.59 +/- 0.18 L), and PaCO2 (44 +/- 9 versus 45 +/- 7 mm Hg). Blood theophylline levels and nutritional status were also similar in both groups. Baseline ET (2.9 +/- 0.6 versus 3.8 +/- 1.6 min) and Pdimax (45 +/- 15 versus 56 +/- 18 cm H2O) were decreased in both groups. Baseline TTdi was high but similar in both groups; at rest the values were 0.15 +/- 0.05 versus 0.16 +/- 0.04, and at end-exercise they were 0.17 +/- 0.06 versus 0.21 +/- 0.12. After treatment FEV1 and Pdimax remained unchanged, but the patients in both groups manifested clinical improvement and had a significant increase in mean ET (Group I from 2.9 to 6.9 and Group II from 3.8 to 6 min, p less than 0.01). TTdi decreased both at rest (0.14 +/- 0.07 versus 0.13 +/- 0.04) and at end-exercise (0.14 +/- 0.06 versus 0.15 +/- 0.09) with no difference between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Obstruction↗
PubMed1988

Ventilatory muscle recruitment during unsupported arm exercise in normal subjects.

To test the hypothesis that during unsupported arm exercise (UAE) some of the inspiratory muscles of the rib cage partake in upper torso and arm positioning and thereby decrease their contribution to ventilation, we studied 11 subjects to measure pleural (Ppl) and gastric (Pga) pressures, heart rate, respiratory frequency, O2 uptake (VO2), and tidal volume (VT) during symptom-limited UAE. We used leg ergometry (LE) as a reference. Exercise duration was shorter for UAE vs. LE (207 +/- 67 vs. 514 +/- 224 s, P less than 0.05) even though the end-exercise VO2 was lower for UAE (9.3 +/- 1.1 vs. 30.8 +/- 3.2 ml.kg-1.min-1, P less than 0.05). Eight subjects had positive Ppl-Pga slopes and less negative end-inspiratory Ppl during UAE vs. LE (-11.8 +/- 6 vs. -19 +/- 7 cmH2O, P less than 0.05). This was not due to the lower VT's achieved during UAE, since at a similar VT, UAE resulted in a rightward and downward displacement of the Ppl-Pga slopes. Three of the subjects had irregular breathing rhythm and negative Ppl-Pga slopes as early as 1 min after initiation of UAE. They had shorter UAE duration and more dyspnea than the eight with positive Ppl-Pga slopes. In most subjects UAE decreases the ventilatory contribution of some of the inspiratory muscles of the rib cage as they have to partake in nonventilatory functions. This results in a shift of the dynamic work to the diaphragm and abdominal muscles of exhalation. In a few subjects UAE results in an irregular breathing pattern and very short exercise tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Respiratory muscle dysfunction secondary to chronic tracheostomy tube placement.

In patients requiring periodic mechanical ventilation, a deflated, fenestrated tracheostomy tube may impair respiratory muscle performance during spontaneous breathing. We describe a patient with severe chronic airflow obstruction (CAO) whose respiratory muscle performance and exercise duration improved after tracheostomy tube removal. Duty cycle, Pdi/Pdi max, and the tension time index were all lower during exercise after tracheostomy tube removal. We conclude that a deflated and fenestrated tracheostomy tube significantly increases airways resistance and can further limit ventilatory muscle performance in patients with airflow obstruction. Patients requiring intermittent ventilatory support may benefit from permanent tracheostomy fistulas that allow for intermittent self cannulation. This would avoid loading of the respiratory muscles when breathing spontaneously.

Airway Obstruction↗
PubMed1983

Cardiac function in sickle cell anemia.

Although ventricular dysfunction is suspected to underlie congestive heart failure in sickle cell anemia (SCA), ejection indexes of left ventricular (LV) pump performance have been found to be normal. The increased preload and decreased afterload of SCA increases the ejection phase indexes and might obscure true LV dysfunction. Therefore, the preload and afterload independent end-systolic stress-volume index was compared in 11 patients with SCA and in 11 normal volunteers. End-systolic pressure and echocardiographic LV dimensions were determined during rest, leg raise, hand-grip and amyl nitrite inhalation. Systemic vascular resistance (afterload) was decreased to 1,033 +/- 314 dynes s cm-5 (mean +/- standard deviation) in SCA from 1,701 +/- 314 dynes s cm-5 in normal subjects. End-diastolic volume index (preload) was increased to 102 +/- 24 ml/m2 in SCA from 66 +/- 10 ml/m2 in normal subjects. Cardiac index was increased to 4.7 +/- 1.1 liters/min/m2 in SCA from 2.8 +/- 0.8 liters/min/m2 in normal subjects. Ejection fractions were similar: 0.59 +/- 0.09 in SCA versus 0.62 +/- 0.07 in normal subjects. However, in patients with SCA, the ratio of resting end-systolic stress-volume index was decreased (1.5 +/- 0.5 in SCA versus 2.8 +/- 0.6 in normal subjects) and the slope of the end-systolic stress versus end-systolic volume index relation was decreased (2.7 +/- 1.3 in SCA versus 4.4 +/- 1.8 in normal subjects), suggesting LV dysfunction in those patients. Thus, LV muscle contractile performance is depressed in SCA. Increased preload and decreased afterload compensate for the LV dysfunction and maintain a normal ejection fraction and high cardiac output.

Adolescent↗